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From "Dan Hecht (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-4813: Round on divide and multiply
Date Thu, 02 Mar 2017 16:14:23 GMT
Hello Impala Public Jenkins,

I'd like you to reexamine a change.  Please visit

    http://gerrit.cloudera.org:8080/6132

to look at the new patch set (#15).

Change subject: IMPALA-4813: Round on divide and multiply
......................................................................

IMPALA-4813: Round on divide and multiply

Address rounding on divide and multiply when results are truncated.

Testing: Manually ran some divides that should overflow, then added
the results to the test.  Made the decimal-test use rounding behavior
by default, and now the error margin of the test has decreased.

Initial perf results:

Multiply is totall uninteresting so far, all implementations
return the same values in the same time:

+-------------------------+-----------------------------------+
| sum(l_quantity * l_tax) | sum(l_extendedprice * l_discount) |
+-------------------------+-----------------------------------+
| 61202493.3700           | 114698450836.4234                 |
+-------------------------+-----------------------------------+
Fetched 1 row(s) in 1.13s

Divide shows no regression from prior with DECIMAL_V2 off:

+-----------------------------+-----------------------------------+
| sum(l_quantity / l_tax)     | sum(l_extendedprice / l_discount) |
+-----------------------------+-----------------------------------+
| 46178777464.523809516381723 | 61076151920731.010714279183910    |
+-----------------------------+-----------------------------------+
before:  Fetched 1 row(s) in 13.08s
after:   Fetched 1 row(s) in 13.06s

And with DECIMAL_V2 on:

+-----------------------------+-----------------------------------+
| sum(l_quantity / l_tax)     | sum(l_extendedprice / l_discount) |
+-----------------------------+-----------------------------------+
| 46178777464.523809523847285 | 61076151920731.010714285714202    |
+-----------------------------+-----------------------------------+
Fetched 1 row(s) in 16.06s

So the performance regression is not as bad as expected.  Still,
divide performance could use some work.

Change-Id: Ie6bfcbe37555b74598d409c6f84f06b0ae5c4312
---
M be/src/exprs/aggregate-functions-ir.cc
M be/src/exprs/decimal-operators-ir.cc
M be/src/exprs/expr-test.cc
M be/src/runtime/decimal-test.cc
M be/src/runtime/decimal-value.h
M be/src/runtime/decimal-value.inline.h
M be/src/runtime/types.cc
M be/src/runtime/types.h
M be/src/util/bit-util-test.cc
M be/src/util/bit-util.h
M be/src/util/string-parser.h
M testdata/workloads/functional-query/queries/QueryTest/decimal-exprs.test
12 files changed, 861 insertions(+), 426 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/32/6132/15
-- 
To view, visit http://gerrit.cloudera.org:8080/6132
To unsubscribe, visit http://gerrit.cloudera.org:8080/settings

Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Ie6bfcbe37555b74598d409c6f84f06b0ae5c4312
Gerrit-PatchSet: 15
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Zach Amsden <zamsden@cloudera.com>
Gerrit-Reviewer: Dan Hecht <dhecht@cloudera.com>
Gerrit-Reviewer: Impala Public Jenkins
Gerrit-Reviewer: Michael Ho
Gerrit-Reviewer: Michael Ho <kwho@cloudera.com>
Gerrit-Reviewer: Zach Amsden <zamsden@cloudera.com>

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